This invention relates to a method for making nitrodiarylamines, useful as intermediates for preparing dyestuffs and antidegradants. For example, 4-nitrodiphenylamine is used as an intermediate in preparing antiozonants useful in rubber compounds.
It is known to make nitrodiarylamines from nitrohaloarenes and N-acylaromatic amines or other activated forms of the amines in the presence of a so-called acid acceptor, for example, sodium carbonate. This process suffers from disadvantages, since it requires large amounts of the "acid acceptor" and large amounts of by-products are formed.
An improved process is shown in U.S. Pat. No. 4,187,248, in which process a nitrohaloarene, such as p-nitrochlorobenzene is reacted with a sodium, potassium, rubidium or cesium salt of the formyl derivative of an aromatic primary amine, such as potassium formanilide. The process is a batch reaction, and is exothermic, and since all of the reactants are present in the reactor from the outset, temperature and the rate of reaction are difficult to control.